Gurjeet Singh <singh(dot)gurjeet(at)gmail(dot)com> writes:
> Can somebody explain why a standalone count(*) returns 1?
> postgres=# select count(*);
> count
> -------
> 1
> (1 row)
The Oracle equivalent of that would be "SELECT count(*) FROM dual".
Does it make more sense to you thought of that way?
> I agree it's an odd thing for someone to query, but I feel it should return
> 0, and not 1.
For that to return zero, it would also be necessary for "SELECT 2+2"
to return zero rows. Which would be consistent with some views of the
universe, but not particularly useful. Another counterexample is
regression=# select sum(42);
sum
-----
42
(1 row)
which by your argument would need to return NULL, since that would be
SUM's result over zero rows.
regards, tom lane